public class ExString {
    static int bin2Dec(String biNum) throws BinaryFormatException {
        int time = 0;
        int ret = 0;
        for (int i = biNum.length() - 1; i >= 0; i--) {
            char ch = biNum.charAt(i);
            if (ch != '0' && ch != '1') {
                //为输入方便，允许字符串内包含空格
                if (ch == ' ') continue;
                else throw new BinaryFormatException();
            }
            int digit = ch - '0';
            ret += digit * Math.pow(2, time++);
        }
        return ret;
    }
}

class BinaryFormatException extends Exception {
    //Throwable的detailMessage成员为私有
    BinaryFormatException(String msg) {
        super(msg);
    }

    BinaryFormatException() {

    }
}
